It would mean that Sony might get one extra purchase from a person who most likely wouldn't have bought the PS3. Sigh...
I don't know how much of a global impact it will have, it all depends on how Sony markets the game and how many of the game's fans already own a PS3. Even though the game has Disney characters and is loved by many more casual gamers, I doubt Sony will be able to take any significant cut into the casual gamer market with this game alone.
In the end the deciding factors will be how many KH fans already have a PS3, and how many of them (who don't own a PS3) will be willing to buy a PS3 to play it. Considering the price tag of the system...I'm doubting that there will be a huge influx of people buying a PS3 solely to play that game. Then again, it is definitely a nice incentive for those who are sitting on the fence or thinking of buying a PS3.
